In microcomputer systems there are often two or more independent operations occurring at the same time. These operations may be monitored and/or controlled by a single processor. In such a case there are priorities assigned to the various operations. It is important that data involving high priority operations not be lost in the situations where conflicts exist between operations. Circuitry for implementing such prioritizing systems is typically quite involved. Circuitry which can be useful in such priority systems is, consequently, desirable.